Precision method and means for positioning contact points in miniature electrical relays

ABSTRACT

A small cylindrical hardened steel drive shaft having knurled serrations formed circumferentially in a continuous band around a central portion is rotatably mounted in bearing recesses formed in a molded plastic base of a miniature relay adjacent and at right angles to a contact pin hole formed in the base. A contact supporting pin inserted through the pin hole is brought into forced engagement with the serrated portion of the drive shaft which, when rotated, forms racklike mating serrations in the engaging surface of the relatively softer contact supporting pin. A wrench-engaging head formed on the external end of the drive shaft enables partial rotation of the drive shaft to impart linear motion of the order of 0.00005 inch, or less, to the contact supporting pin during final assembly of the relay. After all pins have thus been precisely positioned epoxy is applied to the drive shafts and pins to set and seal them in final position.

United States Patent [72] Inventor Nathan H. Magida Westport, Conn.

[21 Appl. No. 884,987

[22] Filed Dec. 15, 1969 [45] Patented Nov. 30, 1971 [73] AssigneeThermosen, Incorporated Stamford, Conn.

[54] PRECISION METHOD AND MEANS FOR POSITIONING CONTACT POINTS INMINIATURE 2,862,073 ll/l958 Brutscher ZOO/153.16

Primary Examiner-Harold Broome Attorney-Robert A. Buckles ABSTRACT: Asmall cylindrical harderied steel drive shaft having knurled serrationsformed circumferentially in a continuous band around a central portionis rotatably mounted in bearing recesses formed in a molded plastic baseof a miniature relay adjacent and at right angles to a contact pin holeformed in the base. A contact supporting pin inserted through the pinhole is brought into forced engagement with the serrated portion of thedrive shaft which, when rotated, forms racklike mating serrations in theengaging surface of the relatively softer contact supporting pin. Awrench-engaging head formed on the external end of the drive shaftenables partial rotation of the drive shaft to impart linear motion ofthe order of 0.00005 inch, or less, to the contact supporting pin duringfinal assembly of the relay. After all pins have thus been preciselypositioned epoxy is applied to the drive shafts and pins to set and sealthem in final position.

PRECISION METHOD AND MEANS FOR POSITIONING CONTACT POINTS IN MINIATUREELECTRICAL RELAYS BACKGROUND AND OBJECTS OF THE INVENTION The inventionis directed to an improved method of accurately positioningelectromagnetic reeds and contact points in miniature electrical relays,and precision adjusting means for this purpose incorporated in suchrelays during their manufacture. The method and means of this inventionrepresent improved techniques for the assembly of miniatureelectromagnetic reed relays of the type disclosed in my U. S. Pat. No.3,425,008 which issued Jan. 28, 1969 and is assigned to the sameassignee as the present application.

A major problem in the manufacture of miniature relays of this type isthat of precisely positioning the reeds and contacts during assembly,and of holding these parts in the proper relative positions during'theremaining steps of manufacture and during the service life of thedevice. The objective is to establish relay performance in terms ofprecisely specified contact operating and release times, sensitivity,and contact gaps, and to maintain that adjustment of the relativepositions of the parts through subsequent variations in the ambientpositions of the relay, as well as variations in ambient temperatureduring the remaining stages of manufacture and final use of the relay.For example, these precisely positioned internal elements must be ableto withstand moderate ranges of ambient temperature during final.encapsulation in epoxy, and they must also withstand the relativelysevere thermal shocks and stresses of being mounted on and soldered toprinted circuit cards.

The prior art technique of assembly and adjustment outlined in myabove-identified patent involved inserting the contact pins throughrelatively tight-fitting holes in a molded plastic base, and thenpushing them into the desired relative positions by engagement with aprecision external fixture, after which epoxies were poured and curedaround the pins to hold them in place. This was not an entirelysatisfactory procedure because it proved very difficult to maintainthese extremely critical adjustments while the epoxy was being cured. Italso proved to be very dift'icult to obtain an epoxy resin that wouldunaided support the pins adequately through the thermal shock of aprinted circuit soldering operation. The degree of accuracy required inpositioning these contact elements is of the order of less than oneten-thousandth of an inch, i.e., a change of position of oneten-thousandth of an inch is intolerable.

Accordingly it is an object of the invention to solve the problems ofaccurately adjusting the contact elements of miniature relays duringmanufacture.

Another object is to provide a method and means for rapidly andprecisely positioning such elements to a very close tolerance.

A further object is to provide means for securing and maintaining suchprecise adjustments in miniature relays.

An overall object is to produce superior miniature reed relays capableof maintaining desired operating characteristics regardless of physicalorientation or substantial variations in ambient temperature.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others, and theapparatus embodying features of construction, combinations of elementsand arrangement of parts which are adapted to effect such steps, all asexemplified in the following detailed disclosure, and the scope of theinvention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

FIG. I is a perspective view of a completely assembled relay here shownenlarged to several times actual size,

FIG. 2 is an enlarged cross-sectional view of the relay of the inventiontaken along the line 2-2 of FIG. 1 and here shown approximately 10 timesactual size,

FIG. 3 is an enlarged bottom view of a portion of the relay structuretaken along the line 3-3 of FIG. 2,

FIG. 4 is an enlarged view similar to FIG. 3 showing an alternativeembodiment of pin engaging drive shaft, and

FIG. 5 is a greatly enlarged portion of FIG. 3 showing the manner inwhich knurled portions of a drive shaft engage the surface of a contactpin.

BRIEF DESCRIPTION OF THE INVENTION The objects of the invention aregenerally achieved by incorporating adjustable fixtures into the base ofthe relay adjacent to and in engagement with each of the relay contactelement supporting pins. Each fixture comprises a hardened steel driveshaft having a head portion engageable by an external wrench and aknurled portion engaging the surface of a contact supporting pin. Theaxis of the drive shaft is at right angles to the axis of the contactsupporting pin, whereby rotation of the drive shaft imparts linearmotion to the pin causing it to slide in its mounting hole.

DETAILED DESCRIPTION Referring now in greater detail to FIG. I and FIG.2 of the drawing, a miniature relay manufactured according to theinvention and indicated generally at 10 comprises a molded plasticrectangular body or housing portion 11 having a cover member 12 whichmay be formed of either metal or plastic. A plurality of pin terminals13-18 in FIG. 1 protrude from the bottom of relay I0 and are adapted forsoldering to a printed circuit board. Hexagonal-headed drive members 19,20 and 21 are mounted in the bottom of housing 11 in recesses 22, 23 and24 where they are accessible during assembly with the aid of a suitablewrench.

The internal construction of relay I0 is indicated by thecross-sectional view of FIG. 2 where reference numeral 25 represents therelay operating coil having a magnetic pole piece 26 in proximity to aU-shaped magnetic member 27 which is secured to a flexible nonmagneticcontact reed 28, which in turn is mounted on the upper end of contactpin 16. The upper end of contact pin 14 is bent into a horizontalposition as shown at 29 in FIG. 2 and in the preferred embodimentillustrated forms a normally open contact with reed member 28. The upperend 30 of contact pin 15 is bent to the left as shown in FIG. 2 into asubstantially horizontal position and forms a normally closed contactwith reed 28. To operate the relay 10 low voltage electrical power isapplied to the coil 25 through external contact pins 17-18. When coil 25is thus energized magnetic fiux from pole piece 26 attracts magneticmember 27 thereby flexing reed 28 upwardly as shown in FIG. 2 andcausing it to break contact with end 30 and to close contact with end29. When coil 25 is deenergized the spring tension of reed 28 breaks thecontact with end 29 and restores contact with end 30 as shown in FIG..2.The contact pins 14, 15 and I6, and their contact members 28, 29 and 30are preferably formed of a silver magnesium nickel alloy and are goldplated to prevent corrosion and to assure maximum electricalconductivity. As shown in FIG. 2 contact pins l4, l5 and 16 are passedthrough tightly fitting holes 31, 32 and 33 in the base of moldedplastic housing 11. As shown in FIG. 2 and FIG. 3 a recessed well 34 isformed in the bottom surface of housing 11 surrounding pin 14 and drivemember 19. Corresponding recesses 35 and 36 surround pins 15 and 16, andreceive drive members 20 and 21.

Referring now to FIG. 3 of the drawing, the configuration of the drivingmember 19 and the manner in which it is journaled in molded plasticmember 11 will be described. Driving member 19 is formed with twocoaxial smooth cylindrical portions 36 and 37 which bear uponcorresponding semicylindrical bearing surfaces 38 formed in the welledrecess 34 of housing 1 1. The external end of driving member 19 isformed into a hexagonal head portion 39 which rests upon an annularshoulder 40 in counterbore recess 22 within the sidewall of housing 11.Between the cylindrical bearing portions 36 and 37 of drivingmember 19are a pair of raised annular knurled sections 41 and 42 accommodated ina deeper well portion 43 of molded recess 34, whereby the driving member19 may be rotated in its bearing journal without any interferencebetween the raised knurled sections 41-42 and housing 11.

In assembly of the contact pins and adjustable drive means according tothe invention, drive member 19 is placed in its semicylindrical bearingcradle 33 within recess 34 and two drops of thermosetting epoxy resin 44and 45 are applied to the smooth cylindrical bearing portions 36 and 37and to the adjacent exterior surface of housing 11. For this purpose Iuse a high-viscosity low-temperature epoxy which quickly cures at roomtemperature. When the epoxy dabs 44 and 45 have set, a suitable wrench(not shown) is engaged with the head 39 of member 19 and a slightrotational force is sufficient to break the seal between the smoothsurfaces 36 and 37 of member 19 and the cured epoxy 44 and 45, withoutaffecting the bond between the epoxy and the molded plastic housing 11.The drive member is now rotatably retained within its molded plasticbearing journal. Next the straight end of contact pin 14 is insertedinto guide hole 31 from within the main cavity 46 (FIG. 2) of thehousing 11, and the pin 14 is forced downwardly through guide hole 31and past the raised knurled portions 41 and 42 of rotatable drive member19. Because the metal alloy of the pin 14 is softer than the hardenedsteel of drive member 19 the raised serrated portions of knurledsections 41 and 42 cut into the otherwise cylindrical surface of pin 14forming corresponding serrations thereon as shown at 48 in FIG. 2. Thusthis substantially linear serrated surface 48 of pin 14 becomes ineffect a rack engaging corresponding annular serrations 41 of drivemember 19, and the two parts are enabled to function cooperatively inmuch the manner of a rack and pinion. Now when the drive member 19 isrotated in a clockwise direction as viewed in FIG. 2 the contact pin 14is driven upwardly through the exterior wall of housing 11 to increasethe gap between contact members 28 and 29. Conversely, if drive member19 is rotated counterclockwise contact pin 14 is moved downwardly toreduce the gap between contact members 28 and 29.

Because the raised annular surfaces 41 and 42 of drive 19 are veryfinely knurled, these surfaces contain a multitude of very sharp hardpoints which press into the slightly softer contact pin 14 to form anexactly corresponding multitude of toothlike impressions, thereby makingpossible very fine and precise adjustments of contact position throughslight rotational adjustment of exterior drive member 19. Also theforced engagement of contact pin 14 with the serrated surfaces of drivemember 19 effects a strong clamping engagement of these two parts withinthe molded plastic housing 11, thereby maintaining sturdy rigidity ofthe contact elements during the final stages of relay assembly.

To further enhance rigidity, stability, and linearity of contact pinpositioning, I form the contact pin holes through housing 11 with twononcylindrical flat wall portions 50 and 51 angularly disposed oppositeto the serrated engaging portion of drive member 19, as is more clearlyshown by the greatly enlarged cross-sectional view of FIG. 5. With thisconstruction the force of engagement between contact pin 14 and theraised serrated portions 41 and 42 of drive member 19 causes elasticdeformation of the molded plastic material adjacent surfaces 50 and 51thereby obtaining a tighter engagement between the contact pin and thehousing 11.

FIG. 4 of the drawing discloses an alternative construction of the drivemember 19 wherein only a single annular raised collor portion 52 isprovided with a serrated surface for cooperative engagement with acontact supporting pin such as 14. While this construction has provenperfectly operable in tests, and is clearly within the scope of theinvention, I prefer the dual serrated raised annuli construction of FIG.3.

For precisely determining the desired positioning of internal contactssuch as 29 in FIG. 2, therelay coil 25 is energized with a low-voltagesquarewave form signal of predetermined periodicity. The coil energizingsignal is also applied to the horizontal sweep circuit of a cathode rayoscilloscope (not shown), and the transfer contact terminals 14, I5 and16 are connected to the vertical deflection circuit of the oscilloscope.The horizontal trace then appearing on the oscilloscope represents thetime duration of the applied square wave pulses, and since this factorhas been predetermined the horizontal trace can be accurately calibratedin milliseconds. The operate and release times of the relay transfercontacts appear as vertical deflections on the horizontal trace and aremeasured by the horizontal displacement therebetween. By slight turningadjustments of a wrench engaging the hexagonal heads of drive members19, 20 and 21 while the relay is so connected and operated, the desiredoptimum operate and release times may be accurately and quickly set.This method of precise adjustment is easily performed by a relativelyunskilled operator who may become familiar with the procedure in amatter of minutes, thus enabling rapid and economical precisionproduction of an assembly line basis. When the relays have been soadjusted a low-temperature thermosetting epoxy resin is applied overeach drive member and around the base of each externally extendingcontact pin to substantially fill the recess wells 34, 35 and 36, thuseffectively sealing and locking the pins and drive members in theirfinal positions. Following this operation the contact enclosing chamber46 (FIG. 2) is evacuated and degased, back filled with an inert gas andsealed, and the relay assembly is completed.

It is to be understood that while the above description has referred indetail to the adjustment of three contact supporting pins 14, 15 and 16,the present commercial embodiment of the relay 10 includes threecorresponding sets of contact pins and drive means (not shown) to form adouble-pole-doublethrow Form C relay. Of course the method and means ofthe invention may be employed in any desired type'of relay, or any otherdevice where rapid and accurate precision adjustments of the relativepositions of parts may be required.

For the molded plastic body or housing portion 11 I prefer to useglass-filled, or glass-reinforced, diallyl phthalate, which is a readilyavailable thermal setting material having excellent physical andelectrical characteristics. For the contact pin members such as 14, 15and 16 I use gold-plated silver magnesium nickel alloy. And for thedrive members such as 19, 20 and 21 I use a low-carbon screw machinesteel stock, such as employed in the manufacture of Allen wrenches.After machining the drive members are case hardened and gold plated toprevent corrosion.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in carrying out the above method andin the article set forth without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawing shall be interpreted asillustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention which,as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. In an electromagnetic relay having a magnetic core, an electricallyconductive coil surrounding said core, at least one fixed electricalcontact, at least one electrically conductive armature movable to andfrom electrically conductive contacting engagement with said fixedcontact, the combination comprising: an insulating external housing, amember slidably inserted through a restricted aperture in saidinsulating housing and supporting said fixed contact on one end thereofwithin said housing, a rotatable drive member journaled in saidinsulating housing adjacent and substantially at right angles to saidcontact supporting member, and a band of serrated protrusions on saidrotatable drive member forcibly engaging with a linear portion of saidcontact supporting member whereby corresponding serrated indentationsare impressed into the linear surface of said contact supporting memberupon rotation of said drive member.

2. In an electromagnetic relay having an insulating exterior wall, meansfor adjustably positioning internal contact members comprising incombination:

A. a plurality of metallic contact supporting pin members, each saidmember extending through a separate mounting hole in an exteriorinsulating wall of said relay,

B. a plurality of rotatable hardened metallic driving shafts journaledin recesses in said exterior insulating wall, each said driving shaftadjacent to and in forced engagement with one of said pin members, therotatable axis of each said driving shaft substantially at right anglesto said adjacent pin member, and

C. knurled serrations formed on a portion of each said driving shaft inforced engagement with a linear portion of said adjacent contactsupporting pin whereby rotation of said driving shaft impressescorresponding serrations into the linear surface of said adjacentcontact supporting pin and imparts linear sliding motion to saidadjacent .pin in its mounting hole through said relay wall.

3. The combination of claim 2 and,

D. clamping means applied to said driving shafts and supporting pins toprevent relative motion therebetween after their adjustment topreselected positions.

4. In an electrical relay device means for precisely adjusting therelative positions of a plurality of internal contact memberscomprising, in combination:'

A. an insulating wall member,

1. a plurality of linear mounting holes through said wall membercorresponding to said plurality of contact members,

2. a plurality of recesses formed in said wall member adjacent saidmounting holes,

B. a plurality of metallic contact supporting shafts each having alinear portion adapted to fit snugly in said mounting holes,

1. each said shaft extending through a separate one of said mountingholes,

C. a plurality of rotatable hardened metallic drive members eachjournaled in a separate one of said recesses in said wall member,

l. each said drive member positioned adjacent to and in forcedengagement with one of said linear shafts,

2. said drive members each having an axis of rotation substantially atright angles to the axis of said adjacent linear shaft,

3. the portion of each said drive member in engagement with said shaftsbearing annular knurled serrations, and

4. an externally accessible tool-engaging head formed on one end of eachdrive member whereby rotation of said drive members imparts linearmotion to the adjacent linear shafts while impressing correspondingserrations into the engaged portion of said shafts.

5. The combination of claim 4 wherein the linear portions of saidcontact supporting shafts and said mounting holes are substantiallycylindrical and of substantially the same diameter.

6. The combination of claim 4 wherein the cross section of said contactsupporting shafts is nonconforming to the cross section of said mountingholes and the engagement of said shafts with said mounting holesproduces elastic deformation of a portion of said insulating wall memberadjacent a portion of said shafts opposite to the portions of saidshafts engaged by the knurled serrations of said drive members, wherebya tight force-fitting clamping engagement is maintained between saidmembers.

7. The combination of claim 6 wherein said contact supporting shafts arecylindrical, said mounting holes are approximately cylindrical and ofthe same diameter as said shafts but said mounting holes are formed witha pair of planar wall portions forming chords of said approximatelycylindrical holes,

1. In an electromagnetic relay having a magnetic core, an electricallyconductive coil surrounding said core, at least one fixed electricalcontact, at least one electrically conductive armature movable to andfrom electrically conductive contacting engagement with said fixedcontact, the combination comprising: an insulating external housing, amember slidably inserted through a restricted aperture in saidinsulating housing and supporting said fixed contact on one end thereofwithin said housing, a rotatable drive member journaled in saidinsulating housing adjacent and substantially at right angles to saidcontact supporting member, and a band of serrated protrusions on saidrotatable drive member forcibly engaging with a linear portion of saidcontact supporting member whereby corresponding serrated indentationsare impressed into the linear surface of said contact supporting memberupon rotation of said drive member.
 2. In an electromagnetic relayhaving an insulating exterior wall, means for adjustably positioninginternal contact members comprising in combination: A. a plurality ofmetallic contact supporting pin members, each said member extendingthrough a separate mounting hole in an exterior insulating wall of saidrelay, B. a plurality of rotatable hardened metallic driving shaftsjournaled in recesses in said exterior insulating wall, each saiddriving shaft adjacent to and in forced engagement with one of said pinmembers, the rotatable axis of each said driving shaft substantially atright angles to said adjacent pin member, and C. knurled serrationsformed on a portion of each said driving shaft in forced engagement witha linear portion of said adjacent contact supporting pin wherebyrotation of said driving shaft impresses corresponding serrations intothe linear surface of said adjacent contact supporting pin and impartslinear sliding motion to said adjacent pin in its mounting hole throughsaid relay wall.
 2. a plurality of recesses formed in said wall memberadjacent said mounting holes, B. a plurality of metallic contactsupporting shafts each having a linear portion adapted to fit snugly insaid mounting holes,
 2. said drive members each having an axis ofrotation substantially at right angles to the axis of said adjacentlinear shaft,
 3. the portion of each said drive member in engagementwith said shafts bearing annular knurled serrations, and
 3. Thecombination of claim 2 and, D. clamping means applied to said drivingshafts and supporting pins to prevent relative motion therebetween aftertheir adjustment to preselected positions.
 4. In an electrical relaydevice means for precisely adjusting the relative positions of aplurality of internal contact members comprising, in combination: A. aninsulating wall member,
 4. an externally accessible tool-engaging headformed on one end of each drive member whereby rotation of said drivemembers imparts linear motion to the adjacent linear shafts whileimpressing corresponding serrations into the engaged portion of saidshafts.
 5. The combination of claim 4 wherein the linear portions ofsaid contact supporting shafts and said mounting holes are substantiallycylindrical and of substantially the same diameter.
 6. The combinationof claim 4 wherein the cross section of said contact supporting shaftsis nonconforming to the cross section of said mounting holes and theengagement of said shafts with said mounting holes produces elasticdeformation of a portion of said insulating wall member adjacent aportion of said shafts opposite to the portions of said shafts engagedby the knurled serrations of said drive members, whereby a tightforce-fitting clamping engagement is maintained between said members. 7.The combination of claim 6 wherein said contact supporting shafts arecylindrical, said mounting holes are approximately cylindrical and ofthe same diameter as said shafts but said mounting holes are formed witha pair of planar wall portions forming chords of said approximatelycylindrical holes, said planar wall portions angularly and oppositelydisposed from the portions of said shafts engaged by said drive members,and each of said drive members is provided with a pair of axiallyseparated raised annular knurled portions, whereby the serrations ofsaid drive members forcibly engage said cylindrical shafts at two pointsopposite said two planar wall surfaces.
 8. The combination of claim 4and, D. clamping means applied to said drive members and said contactsupporting shafts to prevent relative motion therebetween afteradjustment to preselected positions.